1. Field of the Invention
The present invention relates to an actuator having a slider capable of being reciprocated by a driving action of a driving section.
2. Description of the Related Art
An actuator disposed in a vacuum chamber has been conventionally used for a semiconductor-producing apparatus. The actuator has a slider connected to an external main actuator body through a rod so that the slider can linearly and vertically move in the vacuum chamber. The rod penetrates through a hole defined in a wall of the vacuum chamber. If the hole for the rod to be penetrated therethrough is not sufficiently sealed, the vacuum pressure in the vacuum chamber becomes unstable.
According to the conventional actuator, a seal means such as a bellows is disposed around the outer circumference of the rod. The through-hole for the rod is shielded by the seal means so that the rod can stabilize the vacuum pressure.
According to the conventional actuator, however, when the slider is reciprocated by the driving action of the actuator, the vacuum chamber is under vacuum pressure. By contrast, the bellows for shielding the through-hole for the rod is under atmospheric pressure. Therefore, the expanding force is applied to the bellows based upon pressure difference in and out of the bellows. The durability of the bellows is consequently deteriorated.
Accordingly, a cycle of maintenance such as exchanging the bellows becomes short and efficiency of producing the semiconductor is lowered.
It is a general object of the present invention to provide an actuator which balances the vacuum pressure in a chamber of the bellows and the vacuum pressure in a vacuum chamber and which prevents the bellows from expanding, thereby enabling the durability of the bellows to be improved.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.